Angular fluid mixer



Patented Aug. 11, 1925.

UNITED sTATEs FREDERICK L. CRADDOCK, OI NEW YORK, N. Y.

ANGULAB FLUID MIXER.

Application filed September 15, 1919. Serial 1T0. 323,985.

To all whom it may concern:

Be it known that I, FREDERICK L. Quen- DOCK, a citizen of the United States, residing at New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Angular Fluid Mixers, of which the following is a specification, reference being had therem to the accompanyin drawlngs.

This invention re ates to mixing and agitating liquids.

The problem involved in the mixing of liquids, the dissolving of solids in liquids, the making of emulsions and suspensions, and in the agitating of such blends and suspensions to keep them uniform and of a standard quality is one of obtaining an intimate and uniform blend with a minimum expenditure of time and energy and without the violent beating and local action sought for in churning and in operations where the object is separation rather than combination.

Various types of mixing apparatus are in general use, the most common probably being a vertical cylindrical tank provided with a rotary mixing element extending vertically downward into the tank, the axes of the rotary mixer and the tank being coincident. Such an arrangement serves merely to rotate bodily the entire mass of liquid and is therefore very inefiicient as a blending agency. The use of horizontal rotating paddle wheels, the axes of which extend 1nwardly through the side walls of the tank,

' is also old, but these also do little more than impart rotation to the body of the liquid without breaking up stratification and effecting a blend.

For fairly light liquids, particularly where the depth of the body is nearly equal to the breadth, an improvement upon the foregoing methods has been found in the adaptation of a principle which has been in use for many years-that of placing a propeller upon a shaft passing horizontally through the side of the tank, the propeller being near the tank wall and thrusting straight across. The current thus formed is forced upward upon striking the opposite wall, then back across the top and down to the propeller again, travelling in a substantially vertical plane and leaving the sides of the tank untouched and stagnant. This method has been tried'out in finished sweetened condensed milk in tanks ten feet in diameter, and efi'ected a blend in from two to three hours. It is obvious, however, that a propeller capable of thus turning over so large a bodyof finished milk and of overcoming the choking or retarding effect of the right angled baflle presented by the opposite tank wall must work so hard as to develop a thrashing effect which can do the milk no good.

In connection with this method, another method is worthy of mention in which the propeller is mounted upon a short shaft extending exactly vertically through the center of the bottom of the tank. As may be seen, the directly upward thrust of this pro peller produces a fountain efl'ect which is intended to spread outward in all directions at the top and return via the sides of the tank to the propeller. In light fluids, where the depth of the body about equals the breadth, this method is reported as quite successful, but in so heavy, viscous a product as cold, sweetened condensed milk, and particularly in comparatively shallow bodies where the upward current could hardly distribute itself over the correspondingly large area, this method seems only a little better, by reason of the greater possible speed of the propeller, than the old vertical, overhead driven method previously mentioned.

The object of'the present invention is to devise a method and apparatus for mixing and agitating which shall operate quickly and efiiciently and without beating or severe local action.

The method of this invention comprises essentially a combination of those old and ineflicient methods discussed above. A comparatively rapid transverse current is set up within the body of the liquid or liquids, proceeding from a fixed point relative to the container and at the same time the entire body of liquid is rotated. The result is that the induced flow weaves itself throughout the entire mass of the liquid leaving no stagnant zone and effecting an almost perfect blend in less than one-quarter the time required by the other methods. In practice this result is obtained by mounting a screw propeller within the tank with its axis at an angle to a diameter ,of the tank section at that point. The current induced by the propeller impinges against the opposite wall of the tank at an angle and is deflected. Meanwhile, a slow rotation of the entire mass is set up due to the tangential thrust of the propeller and this combined witlrthe more rapid and direct flow along the axis of the propeller, produces a uniform blend in a surprisingly short time and without any beating or thrashing of the liquids.

In the drawing Fig. 1, illustrates diagrammatically a lan View of one embodiment of my inventive idea. Fig. 2 illustrates diagrammatically a vertical cross-section of Fig. 1, Fig. 3 illustrates diagrammatically a plan view of a modification of my inventive idea and Fig. 4, illustrates diagrammatically a vertical cross-section of Fig. 3. Referring to the drawings and to the embodiment of the inventive idea disclosed therein, 5 is a suitable tank or container through the side of which a suitable bearing 6, is inserted at an angle substantially as illustrated. Carried by the bearing 6, is a propeller shaft 7, secured to which is a suitable propeller or impeller 8, within the tank, the said shaft 7 being provided with means for rotating it, illustrated as a pulley 9. It will be noted that in Fig. 1, the propeller 8,.is so situated within the tank 5, that when same is rotated, material carried by the said tank will be caused also to assume a rotary action. The propeller is so situated as to establish a tangential thrust on the liquid so as to cause the mass to move progressively along the inner surface of the tank wall until it again reaches the propeller where agitation and the said progressive movement is initiated and at the same time the propeller establishes a rapid flow along the axis, which, by virtue of the progressive rotary action, reaches all points in the liquid and acts to blend the component parts thereof. This, it will be noted, is a decided departure from the usual practice and constitutes an important feature of the invention. Further, the propeller 8, is mounted on a relatively long propeller shaft so that it extends a considerable distance into the fluid mass rather than up relatively close to the wall of the vessel as has heretofore been the practice. This permits the propeller to operate at a higher mixing efiiciency. Referring to the side view of Fig. 1, shown at Fi 2, it will be seen that the propeller shaft is in a substantially horizontal position. This is desirable for certain uses although where it is important that the fluid be rapidly passed over the bottom of the vessel during the mixing operation while the mass is also rotated as a whole, the shaft 7 is preferably tilted at an angle substantially as shown in Fig. 4:. By this arrangement, a plan view of which is illustrated in Fig. 3, it will be understood that although the action is quite similar in a general way to that which takes lace in the first instance, it takes place owever, about an axis inclined with respect to the vertical rather than about the vertical axis as in the said former case. Ob-

viously the bearing 6, may be so arranged as to permit ositionlng the propeller shaft 7, at a desired angle in either lane, also it will be obvious that any suitab e design may be employed in constructing an apparatus for accomplishing the purpose desired. The angle at which the axis of the propeller enters the tank is important. It is clear that if this axis were substantially tangential to the container wall, the propeller would act merely to set up the old rotary flow of the entire mass and would do little more than the older devices which have been discussed above. When the axis of the propeller lies along a diameter, it is also inefficient. The best point lies somewhere in between these two extremes, and it has been found best, by practice, to ofi'est the axis .of the propeller only slightly from that of the vertical axis of the container. By this arrangement a rotary movement is effected which is very slow in comparison with the more rapid movement of the liquid through the propeller and along its axis.

By thus placing the axis of the propeller out of alinement with the center of the tank, the direct current flow and the slow rotary movement are both obtained by the same means. If, however, the theory of the weaving current action be sound, it is clear that these two movements might be effected by separate means and the invention in its broad aspects is intended to cover such an arrangement.

On the other hand although the efliciency of this method has been ascribed to the peculiar weaving action of the current combined with the slow rotary motion of the entire mass of liquid itself, the value of the invention is in no wise dependent upon this or any other theory. The facts are that the apparatus, as shown and described, operates to blend and agitate thoroughly and quickly and without subjecting the liquids to injurious beating or severe local action.

The term mixing as used in the appended claims is intended to include both mix- .ing proper and agitation.

The terms liquid or liquids are intended to include all substances acting as liquids whether they be liquids alone or mixtures of liquids with solids or gases.

I claim-- 1. An angular fluid mixer comprising a mixing tank designed to contain a mix and a screw propeller mounted upon a revolvable shaft entering the tank below the level of the mix, away from and parallel with an imaginary vertical plane passing through the centre of the tank.

2. In combination, a tank, a propeller, a propeller shaft, said propeller being adapted to be rotated by the said shaft, cylindrical side Walls for the said tank, said propeller being adapted to be rotated in a vertical plane located parallel to but on one In testimony whereof I hereunto aflix my side of a tank diameter, the axis of rotasignature in the presence of two witnesses. tion being in a vertical plane not corresponding to a tank diameter, but parallel thereto, FREDERICK CRADDOOK' 5 the bottom of the tank bein inclined to the Witn:

plzirlie to the attaching go of the side FRANK D. CHANDLER,

wa s.

Ensm A. BUTLER. 

